The creators of Birds Build Nests return to the field, this time melding verse of varying quality with painstakingly realistic watercolors of approximately 15 species of frogs. The rhyming narrative addresses—somewhat redundantly—how, when, where and why "frogs sing songs." Information embedded in the poems (e.g., that frogs sing "from a pouch in their throats" or that "frogs sing their songs/ When day is no more,/ Hidden by leaves/ On the dark forest floor") receives extensive amplification in a concluding, two-page frog identification guide. Frog aficionados will excuse awkward phrasing ("Frogs sing their songs,/ But polluted dark streams/ Threaten their future/ And our wilderness dreams./ That's why frogs sing songs") for the sake of these endnotes and for Oliver's striking art, which brings the multi-patterned amphibians and their various environments into sharp focus. His detailed work reflects a deep aesthetic appreciation of the natural world. Ages 4-9. (Feb.)